Priority is claimed with respect to Application No. 199 14 068.5 filed in Germany on Mar. 27, 1999, the disclosure of which is incorporated herein by reference.
The invention relates to a method for removing air inclusions between sheets in a stack which is formed by successively feeding and depositing sheets on the stack to be formed. The invention furthermore relates to an arrangement for removing air inclusions when forming stacks from sheets, the arrangement comprising a feeding device for successively feeding sheets to the stack to be formed and on which they are deposited.
As used herein, sheets are understood to mean sheets of paper, carton or plastic, such as foils. The size of these sheets can vary over a wide range. Thus, it is possible with the invention to process sheets of standard copying paper size, as well as sheets that are smaller or several times that size.
During the production of sheets, the sheets are frequently gathered into stacks (also called reams) and are then transported to a further processing location where they are wrapped, for example, with wrapping material. The transport of wrapped stacks requires particular care because individual sheets or whole layers of sheets can easily shift owing to the air inclusions between sheets when the stack is formed. As a result, the stack will lose its desired and mostly quadratic configuration. During the further transport, this can lead to damage that can render the complete stack unusable.
Methods for removing air inclusions in this way are disclosed, for example, in German Patents 195 23 699 A 1 and 34 03 209 A 1, which methods call for pressing or stroking the air out of the completed stacks However, such methods are not optimal.
It is an object of the invention to provide a new and advantageous method, as well as an arrangement, for creating stacks without disturbing air inclusions.
The above and other objects are achieved in accordance with the invention by the provisions of a method for removing air inclusions between sheets in a stack when forming the stack from sheets fed successively by a sheet feeder to the stack to be formed and deposited thereon in a sheet feeding region, comprising: auctioning air out of spaces between the sheets in the sheet-feeding region.
The invention thus provides for suctioning air from the spaces between sheets in the sheet-feeding region where sheets are fed from a sheet feeder for forming a stack of sheets. The mention of suctioned-out air in the following refers to air, which can lead to damaging air inclusions between sheets, or air that is already present between sheets.
One advantageous modification of the method according to the invention consists in suctioning the air from the stack surface located opposite the sheet-feeder. Another advantageous embodiment according to the invention provides that air is suctioned from at least one of the stack surfaces (side surfaces) that extend parallel to the sheet-feeding direction. If two side-by-side arranged stacks are formed, then air can be suctioned respectively from one side surface of a stack by a suction device that is arranged between the stacks. A particularly advantageous embodiment of the method according to the invention provides that the devices for suctioning off the air also perform vibrating movements for aligning the stack surfaces. The effect of suctioning off interfering air can be further improved with the aid of another modification of the invention in that the air above the feeding region is suctioned off because this will remove in a gentle manner the interfering air that is also supplied by the sheets. In the process, air can be sucked through openings in the limiting walls into hollow spaces of suction devices, so-called vacuum chambers.
According to a particularly advantageous modification of the method for suctioning air from the side surfaces of two adjacent stacks, the limiting walls for the hollow if space (vacuum chamber) of a suction device installed between two stacks approach each other and make contact in some locations and are connected in those locations. By providing additional openings with larger cross sections for the air to flow through in the regions of the limiting walls that make contact, undesirable air pressure differences that may occur on both sides of the hollow body can balance out. In order to homogenize the suctioning, it may also be helpful if the flow of air in the hollow space is at least in part reduced or interrupted.
According to another aspect of the invention there is provided an arrangement for removing air inclusions between sheets in a stack during formation of the stack from successively fed sheets deposited on top of one another in a sheet feeding region, comprising: a feeding device for feeding the sheets successively and depositing the sheets on top of one another in the sheet feeding region; and at least one suction device arranged in the sheet feeding region for removing air from intermediate spaces between the sheets.
The invention is preferably used for a feeding device that supplies and deposits the sheets from the side onto the stack, which feeding device can be embodied as a conveyor belt. According to a modification of the invention, the suction device can be characterized by a suction device for removing air from the spaces between sheets, which is assigned to a stack surface opposite the feeding device. However, it can also be assigned to at least one of the stack surfaces that extend parallel to the sheet-feeding direction, preferably both surfaces (side surfaces).
A suction device can be provided with an alignment surface provided with air openings for aligning the sheets of a stack surface. An alignment surface of this type preferably can be combined with a vibrating drive that causes the alignment surface to vibrate.
According to a preferred modification of the invention, an alignment surface can be designed as a limiting wall for a hollow space connected to a vacuum source. When forming two side-by-side arranged stacks to which sheets are respectively supplied, it is particularly advantageous if the hollow space for the suction device has limiting walls with air openings, which are respectively assigned to one side surface of a stack. Such an arrangement for a suction device is particularly space saving and requires little expenditure. The limiting walls for such a suction device can make contact in some locations and can be connected in those locations. The limiting walls preferably can be provided with further openings in the contacting locations, wherein these additional openings have larger cross sections than the other air openings. The hollow space for another embodiment according to the invention can be provided in part with reducing elements for reducing or interrupting the air flow.
According to another embodiment of the invention, the situation concerning air inclusions in the sheet-feeding region can be further improved by arranging an additional suction device above the sheet-feeding region, so that air arriving with the sheets is also suctioned off above the stack.
The invention has the advantage that air inclusions are for the most part prevented during the stack formation. Thus, a later compressing of the stack, which always requires a considerable expenditures is not necessary. The limiting surfaces for the suction devices can also serve as alignment surfaces for the stacks, provided they are induced to vibrate.